Geotechnical Engineering

  Important Question for GTU Exam

  • Define liquid limit of clay. How to obtain liquid limit of clay in laboratory?

  • Write short note on honey comb structure and flocculated structure with neat diagrams.

  • Explain grain size distribution by sieve analysis.

  • What are the different categories of soil water? explain in brief

  • Describe the applications of geology in civil engineering.

  • Calculate the plasticity index, liquidity index and consistency index of a soil mass for a given data. Natural water content: 30%, Liquid limit: 45%, Plastic limit 23%. What would be the type of soil on a plasticity chart?

  • An undisturbed soil sample has total wt of 2060 grams, volume of 1000cc, water content =11 % and specific gravity =2.66. Compute (i) Void ratio, (ii) porosity, (iii) degree of Saturation, (iv) Water content to make sample fully saturated and (v) Efficient unit weight of soil sample

  • The following data were recorded while performing the compaction test:- Water content (%): 7.71 11.5 14.6 17.50 19.50 21.25 Bulk density (kN/m3 ): 17.55 19.50 21.0 20.55 20.30 19.80 Plot the MDD-OMC curve and obtain the optimum water content and maximum dry density. Also plot zero air voids curve. Take G = 2.66

  • Discuss the effects of compaction on various soil properties.

  • What are the purposes of foundation?

  • Different between shallow foundation and deep foundation

  • Explain Culmann’s graphical methods for active earth pressure.

  • What are different factors of safety used in the stability of slopes? Discuss briefly

  • Discuss briefly, different types of slope failures.

  • Define the terms ‘Compression index’, coefficient of volume change’, and ‘coefficient of compressibility’, and indicate their units and symbols

  • What is the coefficient of consolidation? Discuss the Square root time fitting method to determine its value, step-by-step

  • What is Mohr’s strength theory for soils? Sketch typical strength envelop for a clean sand

  • A soil sample 20 mm thick takes 20 minutes to reach 20% consolidation. Find the time taken for a clay layer 6m thick to reach 40% cosolidation. Assume double drainage in both cases

  • Define Earth pressure at Rest. Show the earth pressure distribution on a retaining wall, assuming that the soil fill is dry

  • Enlist various causes for Pre-consolidation of soils. Discuss the Casagrande’s method to determine the pre-consolidation pressure from consolidation test data.

  • A series of direct shear tests were conducted on a soil, each test was carried out till the sample failed. The following results were obtained. Sample No. Normal Stress (kN/m2 ) Shear Stress (kN/m2 ) 1 15 18 2 30 25 3 45 32 Determine the Cohesion and Angle of shearing resistance for the soil

  • The following results were obtained from a series of consolidated undrained (CU) shear tests on a soil, in which the pore water pressure was not determined. Determine the cohesion and the angle of shearing resistance. Sample No. Confining pressure (kN/m2 ) Deviator Stress at failure (kN/m2 ) 1 100 600 2 200 750 3 300 870

  • Discuss the effects of compaction on various soil properties.

  • Differentiate between normally consolidated and over-consolidated soils

  • A retaining wall, 6 m. high, retains dry sand with an angle of friction of 30°, and unit weight of 16.2 kN/m3 . Determine the earth pressure at rest. If the water table rises to the top of the wall, determine the increase in the thrust on the wall. Assume the submerged unit weight of sand as 10 kN/m3

  • Compare the ‘Direct Shear Test’ and ‘Triaxial Compression Test’.

  • With the help of Terzaghi’s Spring Analogy concept, define and explain the phenomenon of consolidation.

  • During consolidation test, the void ratio decreases from 0.80 to 0.50 under the stress increment of 2.0 kg/cm2 to 4.0 kg/cm2 . Compute coefficient of compressibility & coefficient of volume compressibility.

  • A retaining wall of height 6.0 m has a horizontal backfill with C=30 kPa, Φ = 20˚ & γt = 20 kN/m3 . Compute the total passive thrust acting on the wall.

  • Explain the different Triaxial tests which can be performed with the different drainage conditions.

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